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SubjectRE: Topic for discussion: OS Design
FWIW, 'message passing' is the wrong answer to the question 'how do I
separate the components of a kernel into distinct modules for <mumble>' but
that's because it's tied to the Accent ancestry of the Mach style

One of the few things we did get right in Brevix was the idea of an
interface transition that used the memory management architecture of PA-RISC
effectively to give the modularity and production without the overhead of
message passing. If you want someone to add components to hardware to
support that, get them to set up a system that effectively separates memory
addressability from memory accessability, as PA-RISC did. (Oh wait, we did
that. If Intel didn't throw it away, Itanium *will* have such an

Crossing memory protection domains does not need to be slow. It's not in
PA-RISC, although it is in the VAX-ish memory architecture of systems like
x86. It doesn't have to be in IA-64, if one is willing to abandon 'legacy.'

-----Original Message-----
From: Dwayne C . Litzenberger []
Sent: Sunday, October 22, 2000 8:57 PM
To: Erno Kuusela
Subject: Re: Topic for discussion: OS Design

> crossing memory protection domains is slow, there's no way around
> it (except better hardware).

So what we really need to do is get some custom "RAM blitter" into our
hardware to do the memory copies needed for fast context switching and

Too bad nobody on this list works at an electronics design company... ;-P

Dwayne C. Litzenberger -

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